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6 Things to Know When Shopping for a Crawl Space Vapor Barrier

Worker carrying a role of vapor barrier

Understanding the role of a crawl space vapor barrier is crucial to protecting your home from the dampness and darkness concealed beneath. The appropriate barrier shields your home from moisture-related issues, ensures structural durability, and improves air quality. 

In this article, we explain the process of choosing the proper vapor barrier and the importance of crawl space repair for ensuring a healthier living environment in your home. 

What is a Crawl Space Vapor Barrier? 

A crawl space vapor barrier is a near-impermeable protective layer installed to prevent moisture from entering the crawl space beneath a home. It acts as a defense against dampness, mold growth, and potential foundation damage, contributing to the home’s overall health and structural integrity. It also helps deter pests and enhances energy efficiency. 

In North Carolina, crawl space vapor barriers are crucial for safeguarding your home, ensuring your home remains dry and structurally sound. 

How to Shop for a Crawl Space Vapor Barrier

Choosing a suitable crawl space vapor barrier for your home is crucial for adequate protection. Consider these tips when shopping for the best solution for your home. 

1. Consider the Thickness and Material Type of the Vapor Barrier 

Start with the basics—thickness and material type are the initial considerations when homeowners begin researching vapor barriers. These factors ensure the selection of a barrier with optimal durability and moisture protection. 

Selecting the right thickness and material depends on your crawl space conditions and the required protection level. In North Carolina’s humid climate, a 20 mm vapor barrier may be recommended, ensuring optimal durability and preventing crawl space water and vapor intrusion. 

Thickness is measured in millimeters (1/1000th of an inch), and size recommendations vary from 6 to 20 mm, depending on specific crawl space conditions like moisture levels, ventilation, and soil type. Due to increased durability, more robust barriers measuring 20 mm are better suited for humid climates.

Material types differ, with options including high-density polypropylene (HDPE) and polyethylene. The latter being the preferred choice for its superior moisture resistance and durability.  

Contact a professional for an assessment to ensure optimal coverage. 

encapsulated crawl space with floor joists

2. Review the Vapor Barrier Performance Specs 

Choosing a vapor barrier with the right performance specifications ensures a dry and healthy crawl space. 

 Performance specifications, including perm rating, classification, reinforcement, and mildew resistance, are crucial in determining the effectiveness of a vapor barrier. The perm rating reflects a material’s moisture permeability, with a lower rating indicating more effective moisture blocking. 

In North Carolina, where humidity and moisture control are significant concerns given our climate, the optimal perm rating for vapor barriers is 0.1 perm or less. This low perm rating ensures maximum effectiveness in moisture blocking, a crucial factor in safeguarding your home’s structure and indoor air quality from excess moisture and humidity. 

Pro Tip: A vapor barrier with a perm rating of 0.1 or less is classified as a “Class I” vapor retarder, the highest classification for vapor barriers. This rating signifies that the barrier provides the highest level of moisture protection, which is particularly crucial in North Carolina for managing humidity, preventing mildew, and enhancing energy efficiency. 

3. Specify Vapor Barrier Size, Crawl Space Coverage, and Required Accessories 

After determining which vapor barrier type is suitable, the next step is assessing the material size necessary and required installation accessories. 

Begin by determining the necessary amount of material to adequately cover your crawl space. Consider the dimensions of your space, remembering to factor in the overlap between sheets. Also, identify any required installation accessories, such as tapes or adhesives, to ensure a secure fit. 

worker in dark crawl space installing a vapor barrier

4. Account for the Vapor Barrier’s Durability and Maintenance 

Understanding a vapor barrier’s UV resistance and maintenance requirements will help you better understand the future upkeep involved. 

Remember that durability and ease of maintenance are crucial factors. Considering your vapor barrier’s UV resistance and maintenance requirements is essential for longevity. UV-resistant materials are vital for crawl spaces exposed to sunlight, as this protection prevents the material’s degradation over time.  

Additionally, opt for barriers that are easy to clean and maintain, ensuring lasting protection and durability. 

5. Key Factors for Choosing a Vapor Barrier: Warranty, Lifespan, Cost 

Before deciding on a vapor barrier, consider its warranty, lifespan, and cost options. A warranty provides peace of mind; the lifespan indicates how long your investment will last. Balancing these factors with the cost will help you choose a vapor barrier that offers the best long-term value for your home. 

Tar Heel Basement Systems provides premium service, maintenance, and financing plans for our crawl space repair and encapsulation services, ensuring your investment lasts long-term.   

6. Consider North Carolina’s Code Regulations  

Building codes are complex and best left to crawl space professionals. Experts assess and tailor solutions, ensuring your vapor barrier meets your state’s legal requirements. This proactive approach ensures compliance, optimal vapor barrier performance, and a healthier, more resilient home. In North Carolina, proper crawl space floor sealing, coverage, and securely taped seams are essential for effective moisture control and aligning with specific codes. 

Schedule a Free Inspection with Tar Heel Basement Systems Today! 

Tar Heel Basement Systems work truck

Given the complexity of building codes and installation details, we recommend contacting Tar Heel Basement Systems for a free inspection. Our experts will assess your home’s crawl space and recommend the best vapor barrier solution for your North Carolina home. Ensure long-term protection and peace of mind by taking this proactive step towards a healthier and more secure living environment. 


The best vapor barrier meets the specific needs of your crawl space, considering factors like crawl space moisture, humidity levels, and local climate. Contact a professional to ensure your home benefits from tailored advice and proper installation.

Vapor barrier preparation involves cleaning the crawl space, removing debris, and ensuring the ground is leveled before laying the barrier. Vapor barrier installation is best left to crawl space experts, who can ensure proper installation for long-term protection. 

Polyethylene is widely considered the optimal material for vapor barriers, offering moisture protection, durability, chemical resistance, cost-effectiveness, and versatility for crawl space repair.


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